Wikipedia
QuesTec is a digital media company that pioneered virtual replay from real-time measurement data for baseball and tennis. Years before competitors introduced similar products, QuesTec had established a reputation for accuracy and reliability. Although originally based on internally developed technology, in 1998 QuesTec moved to tracking technology provided by engineers at the Atlantic Aerospace Electronics Corporation (now a division of L-3 Communications). QuesTec is best known for its Umpire Information System (UIS), used by Major League Baseball for the purpose of providing feedback and evaluation of Major League umpires.
The QuesTec company, based out of Deer Park, New York, has been mostly involved in television replay and graphics throughout its history. In 2001, however, the company signed a 5-year contract with Major League Baseball to use its pitch tracking technology as a means to review the performance of home plate umpires during baseball games. The contract continued through the 2008 season through annual extensions.